“Soul mate” story where the first thing your soul mate says to you is tattooed on your hand (or their name, or whatever indicator you want, it doesn’t matter) except the pairings don’t indicate compatibility at all. People seem to just be like. Randomly paired up. Traditionalists insist that marriage is for tattoo-defined soul mates but for most people in the modern world meeting your tattoo buddy is like “oh hey, it’s you! That’s neat!”
The careers of multiple scientists are fuelled entirely by trying to figure out what the tattoos actually indicate.